Thermostatic contact mechanism



June 12, 1934. B. E. GETCHELL 1,962,587

THERMOSTATIC CONTACT MECHANISM Filed Mar h 13, 1951 2 Sheets-Sheet l INVENTOR Benjamin E. G tahell,

THERMOSTATIC CONTACT MECHANISM Filed March 13, 1951 2 Sheets-Sheet 2 Laad INVENTOR Ben amin Ge hell,

Patented 1a.. '12, 1934 i 1,962,581 THERMOSTATIC CONTACT MECHANISM Benjamin E. 'Getchell, Plainville, Conn., assignor tofl'he Trumbull Electric Manulacturingcompany,lPlainville, Conn a corporationol Con necticut Application March 13, 1931, Serial No. 522,468

3Clal'ms.

My inventionrelates to electrical contact mak ing devices and particularly to a means for accelerating the action of slow moving electrical contacts at the instant of-making or breaking circuits. The slow movements caused by changes in temperature, pressure, liquid level or mechanical devices make this accelerated contact action ,highly desirable in order to prevent the burning and pitting of contacts.

Such a device may be used for the purpose controlling a circuit which may be a simple battery circuit for operating an alarm or an indicator under predetermined conditions, or it may be used for making or breaking a circuit for operating a relay, a magnet, a motor, etc.

Ordinarily contacts under control of such slow moving apparatus close or open very slowly,.which results in prolonged arcing and consequent damage and short life to the contacts.

Contactors usually consist of one movable and one stationary contact. Sometimes both contacts "are movable. I

The movable contact used for such. purposes is imually mounted on a part of the device, the

5 movement of which is caused by a slow moving mechanism or by a gradual increase or decrease in-temperature or pressure or by a change in liquid level.

In adapting my invention to practice I fasten one end of a relatively thin and narrow bi-metallic strip to either the movable or the stationary contact or, in some instances, such strips may be fastened .to both of the contacts. To the free end of the bi-metallic strip I preferably secure a piece of contact metal such as platinum, tungsten, silver or the like.

To, secure quick closing action the thin bimetallic strip is mounted so that the local heat generated at the instant of contact causes the jstriplto flex toward the engaging contact.

To secure quick opening action the thin bimetallic strip is mounted so as to flex away from the engaged contact in response to a rise in temperature.

5 i In closing or opening a slow moving contact an arc may be established just before the closing or opening is actually completed. This are heats the contact which in turn heats the thin .bi-metallic' strip causing it to quickly bend and thus accelerate the openingor closing action as the case may be.

L By reason of. its quickly-flexing action and its "function to bend away from or toward the stationary contact, thisform o! flexing contact is admirablyadapted to quickly open or to close the circuit and to'reduce any arcing that might be caused by vibration. 1

The thermostatic strip is connected, either directly or through its supporting element, in the w as is the stationary contact and the tunetion of the strip is to open or close the circuit by making or breaking connection with the stationary contact.

The main object of my invention is to provide a simple, positive and inexpensive quick acting contact making or breaking means for use in connection with slow moving mechanisms as herein set forth.

In some instances it is desirable to utilize a bimetallic thermostatic strip as a means for causmg the preliminary movement of the small iii-metallic strip.

Fig. l is an edge view showing one form of thermostatic device embodying my invention and particularly intended to complete a circuit quickly.

Fig. 2 is a similar view of a modification intended to break a circuit with a quick action.

Figs. 3 and 4 are details showing other modifications.

Fig. 5 is a sectional view showing a circuit making and breaking device embodying my invention and actuated by the rise and fall of level of liquid.

Fig. 6 is another modification in which a thermostatic device is actuated by gear mechanism.

Fig. '7 is a diagrammatic view showing the application of a quick-make and a quick-break thermostatic device to the control of an electrovided with a thumb piece or knob 16 by which it may be adjusted. In order to prevent injury 'to the thermostatic strip 12 and to insure permanently conducting contact surfaces I prefer to construct the cdntact points 18 and 19 of such metal as tungsten, platinum, silver or the like.

In the form thus described the. composition of the two sides of the arm-l0 is such that as the temperature goes down the movable end of the arm 10 approaches the stationary contact. The

supplemental thermostatic memberor finger- 12 is so designed (that when it approaches to within arcing distance of the stationary contact, heat is set up so that the tendency of the-finger 12- is to flex and move rapidly toward the stationary contact, thusrefiecting a quick-make and avoiding chattering and deleterious arcing;

' In the construction shown in Fig. 2 the arm 10 is'so constructed that as the temperature rises the movable end moves awayirom the stationary contact member 14. The auxiliary contact finger A thermo- .by means of a nut 24. In this case it will be seen that the auxiliary thermostatic member 21 is carriedby the relatively stationary support in- I stead of by the flexing thermostatic arm 10. The

action, however, is similar to that of the forms shown in Figs. 1 and 2. These parts may be con-' structed' and arranged to open or close the circuit with a quick action.

I In the form shown in arm 10 carries an auxiliary thermostatic finger 25 which coacts with the stationary thermostatic finger 26. The latter may be adjusted by a screw member 27 so as to vary the action of the device.

In the form shown in Fig. 5 the float 30 is supported on liquid 31 in'the receptacle 32. This float 30 carries a thermostatic finger 33 adapted to coact with the point of a relatively stationary contact member 34 carried by'the cover 35 of the receptacle. It will be understood that the stationary and movable contacts are connected in the circuit in any suitable manner and that the thermostatic strip 33 may be constructed so as to move rapidly toward or away from the'stationary contact depending upon the necessities of the case.

In the construction shown in Fig. 6 the arm 37 has one end supported at 38 and an intermediate portion adapted to be engaged by a pin or pro-.

jection 39 carried by the gear 40. The latter-is driven by aworm 41 which thus moves the arm 37 very slowly. The thermostatic finger'42 is carried by the movable end of the arm 37 and adapted to coact with the stationary but adjustable contact carrying screw 43 so that the thermostatic finger 42 has a quick action when heated by the arc. t

In Fig. 'l', I have shown the thermostatic device applied to the control "of the startingand.

stopping circuit of a switch to be used in connection with a heating system where, for instance, some form of electrically driven mechanism, not shown, is employed to feed fuel to a burner or to actuate a damperor similar device. In the drawing line terminals 50, 51 and 52 are connected to a source of power. The heating load is connected to the terminals 53, 54 and 55. Movable switch' members 56, 5'7 and 58 are furnished, all

carried by or actuated by some portion of an electro-magnetic system.

In this case electro-magnetic coil 60 is shown with a solenoid 61 connected to and electrically insulated from the switch members 66, 67 and 68 so that when the magnet is energized the switch circuits are closed. A spring62 tends to open the circuit when the magnet is de-energized. Relays 63 and 64 are connected in two branches of the circuit, as shown in my Patent No. 1,681,851.

An auxiliary switch member 65 controls a circuit from the relay 64 to the thermostatic arm 10. One of the stationary contacts 66 is connected to the coil 60 and the other stationary contact 6'7 is connected to the relay 64. The thermostatic fingers 68 and 69' are carried Fig. 4 the thermostaticby the movable end of the thermostatic arm 10 and adapted to coact with the stationary contacts 66 and 67, respectively, and so constructed that the heating of finger 68 causes it to bend away from contact 66 and the heating of finger 69 causes it to bend toward contact 67.

Thermostatic arm 10 is actuated by room temperature and as the temperature drops it moves I toward contacts 66 and 67, and as the temperature rises it moves away from 66 and 67.

Its operation is as follows: As the temperature drops arm 10 moves toward 66 and 67. During the course of this movement 66 engages 66 but no circuit is completed; a continued movement brings 69within arcing distance of 67. The slight are set up heats arm 69 causing it to bend quickly toward contact 67, thus closing with a'minimum 'period of arcing, a circuit as follows: 50, 63, 60, 66,. 68, 69, 67, 64, 52. This energizes the magnet 60 and closes the load circuit and also shunts the contacts 69 and 67 out of the circuit by closing contacts at 65. Magnet circuit is now as follows: 50, 63, 60, 66, 68, 10, 11, 65, 64, 52 and magnet 60 holds the load circuit closed until the temperature rises to a predetermined point.

As the temperature rises arm 10 slowly bends away from contacts 66 and 67 breaking contact between 69 and 67 first which has no eifect on the circuit, as before mentioned, they are now shunted at 65. A continued movementof the arm 10,5

slowly separates contacts 66 and 68 starting an are between these points. This are instantly heats the thermostatic finger 68 and causes it to bend quickly away from 66 thus'interrupting the circuit of magnet 60 with a minimum period of arcing. Without these quickly bending fingers 68 and 69 thearcing would be greatly prolonged with greatly increased damage to contacts.

It should be understood that other changes may be made in the details of construction and in the arrangement of ,parts, and that the principle of the invention as herein set forth is 'applicable to many diiierent uses of which I merely attempted to indicate'a few.

I claim:

have

. -1. A thermostatic switch including a movable arm, two bimetallic fingers carried thereby, a stationary contact for each finger, one of said fingers being constructed to move away from its contact upon increase of temperature'and the other finger being constructed to move toward the contact upon increase of temperature.

2. A thermostatic switch including a bimetallic arm, movable at one end, two flexible bimetallic fingers carried thereby, a stationary contact for each finger, one of said fingers being'constructed to move away from its contact upon increase of temperature and the other finger being con-- structed to move toward its contact upon increase of 1 temperature.

- 3. An electricalcontacting device including a 1 plurality of stationary contacts, a movable member, a plurality of bi-metallic thermostatic members secured at one end of each to the movable member, the free end of each coacting with one of the stationary contacts, some of said bi-metallic thermostatic members being adapted to move with a quick action to ward itsstationary contact at the instant 01 contact engagement and some of the bi-metallic thermostatic members adapted to move with a quick action away irom its stationary contact at the instant of contact separation.

BENJAMIN l-GL'ICHELL. 

